Endangered Mussel Research Articles

Altered thermoregulation as a driver of host behaviour in glochidia-parasitised fish.

Parasites alter their host behaviour and vice versa as a result of mutual adaptations in the evolutionary arms race. One of these adaptations involves changes in host thermoregulation, which has the potential to harm the parasite and thereby act as a defence mechanism. We used a model of the brown trout (Salmo trutta) experimentally parasitised with glochidia ectoparasitic larvae from the endangered freshwater pearl mussel (Margaritifera margaritifera) to reveal whether parasitisation alters fish behavioural thermoregulation. A study using radiotelemetry temperature sensors was performed during almost one year of the M. margaritifera parasitic stage. Glochidia-infested S. trutta altered their thermoregulation through active searching for habitats with different thermal regimes. The general preference for temperatures in infested fish varied and was either above or below the temperature preferred by uninfested individuals. Infested fish also preferred different temperatures across localities, whereas uninfested fish maintained their thermal preference no matter which stream they inhabited. Glochidia further induced the expression of a behavioural syndrome among S. trutta personality traits, suggesting that it might increase the probability that the fish host would occur in the glochidia temperature optimum. Our findings present the first evidence that thermoregulation plays a fundamental role in the relationship of affiliated mussels and their fish hosts. Incorporating thermoregulation as a factor in the study of this relationship can help to interpret results from previous behavioural studies, as well as to optimise management measures related to endangered mussels.

T/B APEX 3508: Best Practices for Detection and Recovery of Sunken Oil

ABSTRACT On September 2, 2015, two towing vessels collided on the Lower Mississippi River at Mile 937, near Columbus, Kentucky, resulting in the complete breach of the #3 starboard cargo tank on the T/B APEX 3508 and the release of 120,588 gallons of clarified slurry oil (CSO; Group V oil; Specific Gravity: 1.14) into the navigable waterway. The incident was classified as a Major Inland Spill in accordance with the National Oil and Hazardous Substance Contingency Plan and a Major Marine Casualty that was jointly investigated by the United States Coast Guard and the National Transportation Safety Board. Over flights conducted as far as 20 miles downriver indicated only light, sporadic sheening for 1–2 days. On-water and shoreline assessments conducted up to six miles downriver revealed no visible signs of surface oiling. Based on its properties, the vast majority of the CSO was presumed to have sunk, but its precise disposition and location was not confirmed. Using side scan sonar (SSS) technology, two distinct subsurface anomalies with an approximate combined area of 9,200 m2 were identified on the river bed in the vicinity of the incident. The anomalies were confirmed as oil by divers and direct sampling, and were then divided into 25 m grids for identification and tracking. The Unified Command evaluated best available technologies and determined that GPS guided environmental dredging would be the safest, most effective and efficient of the recovery options. The established cleanup endpoint was a maximum of 10% sporadic oil distribution in each grid. Two endangered mussel species were identified as potentially inhabiting the affected area. A diver survey was conducted in the area and concluded that bottom habitat was not likely to support the listed species. Further consultations with the resource manager indicated that proposed recovery operations posed low risk to the species. Recovery operations commenced on September 15, 2015 and concluded on September 25, 2015. Endpoint verification was conducted via SSS. In total, response operations lasted 23 days (eight operational periods), involved over 120 responders and 75 specialized response assets, and cost approximately $5 million. Approximately 2,524 m3 of dredged material (liquid and solids) were removed. After decanting, approximately 1,730 m3of oiled solids representing approximately 50 to 75% of the spilled product was recovered. This case serves as a benchmark for sunken oil detection and recovery operations, and identified many best practices that should be considered on future cases with similar spill conditions.

The endangered thick-shelled river mussel (Unio crassus): a new host species for the European bitterling (Rhodeus amarus)

Large freshwater mussels (Unionoida) are declining throughout the world. The European bitterling Rhodeus amarus (Bloch, 1782) female spawns its eggs inside the unionids’ shells, where fertilisation and further embryonic development take place; thus its reproduction depends fully on the presence of large freshwater mussels. Unio crassus, previously regarded as one of the most numerous unionids in Europe, is now listed in the IUCN Red Data List as being globally endangered. Despite its previous prevalence, it was never reported as a host for the bitterling. A large population of U. crassus was studied in small river at the Świętokrzyskie Mts (Poland), where also electrofishing was conducted. In each bitterling territory located on the study plots, we found individuals of U. crassus, with the bitterling eggs or larvae developing on mussel’s gills. That proves that this species can be also used by the bitterling for reproduction. We suggest that this relationship has not been reported to date due to the mussels’ rarity and ongoing decline. However, it is also possible that the endangered mussel is a novel host for the bitterling, which is expanding its range throughout Europe.

Physical and chemical constraints limit the habitat window for an endangered mussel

Development of effective conservation and restoration strategies for freshwater pearly mussels requires identification of environmental constraints on the distributions of individual mussel species. We examined whether the spatial distribution of the endangered Alasmidonta heterodon in Flat Brook, a tributary of the upper Delaware River, was constrained by water chemistry (i.e., calcium availability), bed mobility, or both. Alasmidonta heterodon populations were bracketed between upstream reaches that were under-saturated with respect to aragonite and downstream reaches that were saturated for aragonite during summer baseflow but had steep channels with high bed mobility. Variability in bed mobility and water chemistry along the length of Flat Brook create a “habitat window” for A. heterodon defined by bed stability (mobility index ≤1) and aragonite saturation (saturation index ≥1). We suggest the species may exist in a narrow biogeochemical window that is seasonally near saturation. Alasmidonta heterodon populations may be susceptible to climate change or anthropogenic disturbances that increase discharge, decrease groundwater inflow or chemistry, and thus affect either bed mobility or aragonite saturation. Identifying the biogeochemical microhabitats and requirements of individual mussel species and incorporating this knowledge into management decisions should enhance the conservation and restoration of endangered mussel species.

Acute effects of salinity exposure on glochidia viability and host infection of the freshwater mussel Anodonta anatina (Linnaeus, 1758)

Freshwater mussels of the Unionida are globally in decline and knowledge of the sensitivity of their vulnerable life stages to stressors is crucial for their conservation. Increasing salinity, e.g., due to road deicing, has been proposed as an important stressor, but its impact on the complex interaction between mussel larvae and their obligate attachment to fish hosts remains largely unknown. This study tested the acute toxicity effects of environmentally relevant chloride concentrations on larvae of European Anodonta anatina mussel as well as the impacts on attachment rates of the larvae to their fish host. Chloride concentrations above 727mg⋅L−1 significantly affected glochidia viability and the 24h EC50 value was determined at 2505mg⋅L−1. Successful attachment of glochidia to the host fish Phoxinus phoxinus was negatively correlated with increasing chloride concentration and became significant at concentrations >2909mg⋅L−1. Comparable responses could be observed by separately counting fin and gill attached glochidia, while gill attachment showed the highest correlation with overall attachment rates. These results indicate a potential threat from short-term elevated chloride concentrations during runoff events on sensitive life stages of freshwater mussels. Consequently, we propose additional chloride sensitivity tests on other mussel species as well as the reduction of salt peak input loading into freshwater bodies through a 3R-principle (restriction of use, retention of runoff for peak concentration avoidance and replacement by alternatives) in areas where endangered mussels occur. CapsuleFreshwater mussels of the Unionoida are globally in decline and knowledge on the sensitivity of the most vulnerable larval stages to salinity is crucial for their conservation.

Water and Sediment Quality in the Clinch River,Virginia andTennessee,USA, over Nearly Five Decades

AbstractThe Clinch River, in eastern United States, supports a diverse freshwater fauna including endangered mussels. Although mussel populations are stable in the Clinch's northeastern Tennessee segment, long‐term declines have been documented upstream in Virginia. We analyzed water and sediment quality data collected by government agencies from the 1960s through 2013 in an effort to inform current management. The river was divided into sections considering data availability and major tributaries. We tested for spatial differences among river sections and for temporal trends, and compared measured values to potentially protective levels if available. Ammonia concentrations approaching and exceeding protective levels were recorded, most often during the 1970s and 1980s in upstream sections. Sediment metals occurred at levels potentially causing biological effects, mainly during the 1980s and 1990s. In the 2000s, water‐column metals have been well below protective levels for general aquatic life. Dissolved solids (DS) increased in most river sections over the study period but mussel‐specific protective levels are not known. Analysis of waterpH, total N, and total P did not generate conservation concern. Enhanced monitoring for sediment metals, water‐column metals, and ionic composition ofDS; closer alignment of agency water monitoring practices in the two states; and research to determine biological effects ofDSat current and anticipated levels can aid future conservation management.

Understanding Water Column and Streambed Thermal Refugia for Endangered Mussels in the Delaware River

Groundwater discharge locations along the upper Delaware River, both discrete bank seeps and diffuse streambed upwelling, may create thermal niche environments that benefit the endangered dwarf wedgemussel (Alasmidonta heterodon). We seek to identify whether discrete or diffuse groundwater inflow is the dominant control on refugia. Numerous springs and seeps were identified at all locations where dwarf wedgemussels still can be found. Infrared imagery and custom high spatial resolution fiber-optic distributed temperature sensors reveal complex thermal dynamics at one of the seeps with a relatively stable, cold groundwater plume extending along the streambed/water-column interface during midsummer. This plume, primarily fed by a discrete bank seep, was shown through analytical and numerical heat-transport modeling to dominate temperature dynamics in the region of potential habitation by the adult dwarf wedgemussel.

Critical swimming speed of brown trout (Salmo trutta) infested with freshwater pearl mussel (Margaritifera margaritifera) glochidia and implications for artificial breeding of an endangered mussel species

Unionid freshwater mussels need to attach to a host fish for completion of their life cycle. It remains unclear whether the relationship between these mussels and their host fishes can be considered parasitic, mutualistic, or commensal. Herein, we studied the effects of Margaritifera margaritifera infestation on Salmo trutta, the most important host of this endangered mussel species in Central Europe. Glochidial load of host fish increased with increasing glochidial concentration, but the highest ratios of encysted glochidia to exposed glochidia were found at low concentration (15,000 glochidia L(-1)) during infestation. Host fish mortality occurred at infestation rates of ~350 glochidia per g fish weight and was highest (60%) at the highest infestation rates (~900 glochidia per g fish weight). On a sublethal level, swimming performance of hosts was inversely related to infestation rates, with infestation of ~900 glochidia per g fish weight reducing critical swimming speed of S. trutta significantly by ~20% compared to infestation with 6 glochidia per g fish weight. The high mortality and the impaired swimming capability of highly infested hosts indicate a parasitic interaction between M. margaritifera and its host. For conservation and reintroduction of M. margaritifera via glochidia-infested S. trutta, we recommend glochidial loads of 5-100 glochidia per g fish weight, while for artificial breeding of juvenile M. margaritifera under laboratory conditions, higher infestation rates of up to 300 glochidia per g fish weight are ideal to balance high yields of mussels and welfare of host fishes.

My Paddle to the Sea: Eleven Days on the River of the Carolinas * Drifting into Darien: A Personal and Natural History of the Altamaha River

Among the most familiar forms of American nature writing, river narratives have been a dependable subgenre since Henry David Thoreau plied the Concord and Merrimack. Writing about Southern rivers, though, invokes a different heritage. Canonical works like The Adventures of Huckleberry Finn and Life on the Mississippi, along with Deliverance, offer an alternative headwater for contemporary authors. Indeed, the current offerings from John Lane and Janisse Ray are buoyed by their inheritance not only as literary sojourners but also as southerners. In the broadest sense, both authors blend natural and human history with narrative to produce works similar to others devoted to a single river or watershed. Lane's My Paddle to the Sea chronicles a rainy eleven-day river trip down the Santee River system, beginning near the author's home on the Lawson's Fork and continuing on the Broad, Congaree, and Santee, finally terminating at the Atlantic. Ray's Drifting into Darien opens with an abbreviated account of her eight-day exploration of the Altamaha with a group of other naturalists and wilderness enthusiasts. The majority of Ray's book, however, is devoted to small essays on topics related to the river's watershed: the health of Georgia forests, a reconsideration of DeSoto's route through the state, the collection and identification of endangered mussels, to name a few.

Use of Frequency and Duration Analysis for the Determination of Thermal Habitat Thresholds: Application for the Conservation of Alasmidonta heterodon in the Delaware River

AbstractA novel approach for setting thermal habitat recommendations for an endangered aquatic species will be proposed in this paper. The method, uniform continuous above-threshold (UCAT) analysis, evaluates the duration and frequency of continuous events in which the temperature is higher than a specified value and identifies temperature levels that, because of their rare occurrence in the past, can be considered stressor thresholds. The UCAT analysis was applied to set thermal habitat recommendations for Alasmidonta heterodon, an endangered mussel species in the Upper Delaware River. It was found that a maximum daily water temperature of 26.5°C lasting for more than 7 days is a rare event in the A. heterodon population centers in Upper Delaware River and consequently this condition should be avoided by adjusting already regulated cold-water releases from upstream reservoirs. Knowledge of temperature thresholds and their relationship with persistent low-flow periods provided further decision support for...

Parasitism of Mussel Gills by Dragonfly Nymphs

Abstract Predators of unionoid mussels are generally identified as fishes or aquatic mammals. During a mark and recapture study of the critically endangered mussel Popenaias popeii, we discovered a nymph of the dragonfly Gomphus militaris eating the gills of a gravid mussel; larvae and gill material were found in the nymph's gut. Many (15.2%) of the other mussels captured during a quantitative survey exhibited damage consistent with that inflicted by this dragonfly. Few non-gravid mussels were damaged and gravid mussels exhibited substantially more damage in gills used for brooding larvae than in gills not typically used for brooding. This previously unreported parasitic relationship may reflect a unique cost associated with reproduction and should be considered in the development of conservation strategies for P. popeii. Our observations underscore the need for basic ecological data when monitoring endangered species.

Diversity, habitat use and conservation of freshwater molluscs in the lower Guadiana River basin (SW Iberian Peninsula)

Abstract A study on the distribution pattern and conservation of freshwater molluscs of the south Guadiana River (SW Iberian Peninsula) was carried out between the Alqueva dam and the Atlantic Ocean. The knowledge of the distribution and abundance of molluscs before the closure of the Alqueva dam is an important tool for evaluating the potential reduction in diversity and the changes in species conservation status that may occur later. Twenty‐three species (15 gastropods and 8 bivalves) were found in the study area. The presence of Unio crassus and Potomida littoralis indicates the importance of this basin for the conservation of endangered mussels (Unionidae) in the south Iberian Peninsula. Drainage area above the sampling site explained almost 58% of the variation in species richness. Larger drainage areas had a higher number of species, including those endemic to the basin. Patterns of habitat use were examined to identify species preferences with respect to the erosional‐depositional gradient. Islamia minuta, Pisidium casertanum and Pisidium personatum find their optimum habitat in headwaters, whereas Theodoxus fluviatilis, Mercuria emiliana, Radix auricularia and all unionid species inhabit large and stable habitats downstream without marine influence. Populations of invasive Corbicula fluminea were found in the Guadiana River basin, both in rivers with large drainage areas and in brackish waters near the mouths of rivers. Copyright © 2006 John Wiley & Sons, Ltd.

Risk identification associated with iron‐dominated mine discharges and their effect upon freshwater bivalves

AbstractThe controlled release of a partially treated mine‐water discharge dominated by iron was evaluated for impact on the aquatic community during July and August of 1993 in southeastern Ohio. The discovery of an endangered mussel species, Lampsilis abrupta, prompted further validation of a lowest observable effect concentration for the discharge as it was diluted by the Ohio River. In‐stream monitoring detected no significant postrelease responses among individuals of the surrogate species Quadrula quadrula from sites above and below the release. To evaluate the effects of the mine water on bivalve mollusks, laboratory simulation of the controlled release conditions using artificial streams and 30 daily renewals of mine water revealed that cellulolytic activity of Corbicula fluminea was reduced in mine‐water exposures as low as 1.25% (0.19 mg Fe[II]/L). Recovery was evaluated for 30 d after initial exposure and indicated that specific response thresholds for siphoning and bioconcentration were apparent for the bioavailable form of iron and that enzyme activity for exposed Corbicula could return to prestress conditions. Bivalve responses to this threshold limit for the iron‐dominated mine effluent were compared to other standardized test responses (acute and chronic effects using Daphnia pulex, Ceriodaphnia dubia, and Pimephales promelas) and resulted in support of criteria for the bioavailable form of iron at 0.37 mg ferrous iron/L.

Testing the toxicity of sediments contaminated with diesel fuel using glochidia and juvenile mussels (Bivalvia, Unionidae)

Sediment toxicity was evaluated for one site upstream and three sites downstream of a diesel fuel spill that occurred in Fish Creek (OH and IN) in September 1993 using glochidia and juvenile unionid mussels. This fourth order tributary of the St. Joseph River has the only known remaining population of white cat's paw pearly mussel, Epioblasma obliquata perobliqua, and populations of several other federal and state endangered mussels. The impact of the oil spill was of great concern because of the potential long term threat it poses to the survival of these mussels. Sediment samples collected two years after the spill contained low heavy metal concentrations, and detectable, but not quantifiable levels of organic components of diesel fuel. These levels coincided with their lack of toxicity to juvenile Villosa villosa and Lampsilis siliquoidea mussels after 9-day exposures. Fish Creek sediments may be toxic to L. siliquoidea glochidia.

Testing the toxicity of sediments contaminated with diesel fuel using glochidia and juvenile mussels (Bivalvia, Unionidae)

Abstract Sediment toxicity was evaluated for one site upstream and three sites downstream of a diesel fuel spill that occurred in Fish Creek (OH and IN) in September 1993 using glochidia and juvenile unionid mussels. This fourth order tributary of the St. Joseph River has the only known remaining population of white cat’s paw pearly mussel, Epioblasma obliquata perobliqua, and populations of several other federal and state endangered mussels. The impact of the oil spill was of great concern because of the potential long term threat it poses to the survival of these mussels. Sediment samples collected two years after the spill contained low heavy metal concentrations, and detectable, but not quantifiable levels of organic components of diesel fuel. These levels coincided with their lack of toxicity to juvenile Villosa villosa and Lampsilis siliquoidea mussels after 9-day exposures. Fish Creek sediments may be toxic to L. siliquoidea glochidia.

Mercury in hair of muskrats (Ondatra zibethicus) and mink (Mustela vison) from the U. S. Department of Energy Oak Ridge Reservation.

Muskrats (Ondatra zibethicus) are semi-aquatic rodents found throughout most of North America. Muskrats construct extensive burrow systems in the banks of streams and are potentially exposed to environmental contaminants through dermal and dietary sources. Muskrats are primarily herbivorous, which may limit their exposure to contaminants, as most plants contain relatively low concentrations of contaminants. However, riverine muskrats are known to prey on freshwater mussels, and have even been reported to prevent recovery of endangered mussels in the Clinch River of Virginia and Tennessee. Mussels and clams are known to bioaccumulate contaminants to levels several thousand times that of surrounding water, and these contaminants could potentially be bioaccumulated by predatory muskrats. The objectives of this study were to determine hair mercury levels in muskrats and mink inhabiting contaminated sites on the US DOE`s Oak Ridge Reservation. 19 refs., 2 tabs.